The present invention relates to the field of clutch-release bearings, particularly for motor vehicles, of the kind comprising an operating element able to move in translation under the action of a control member such as a clutch-release fork or the piston of a hydraulic control, a thrust rolling bearing intended to act on the clutch-release device of a clutch, such as a diaphragm, and, between the thrust bearing and the operating element, a self-alignment elastic connecting member providing an axial connection between the thrust bearing and the operating element and allowing the thrust bearing to self-centre with respect to the diaphragm if the axis of the diaphragm and the axis the thrust bearing are not exactly coincident at the time of mounting. Such a release bearing is described, for example, in document FR-A-2 663 702.
The rings of thrust rolling bearings are made of pressed sheet metal. The inner ring comprises a radial portion extending outwards in contact with a radial flange of the operating element. The outer ring comprises a radial portion extending inwards for contact with the diaphragm.
The self-alignment elastic connecting member consists or an elastic sleeve lying between he bore of the non-rotating ring of the thrust bearing and a cylindrical bearing surface of the operating element. The sleeve, generally made of elastomere or of some equivalent flexible material, comprises in its bore a number of ribs which protrude radially with respect to the bore and run axially along he length of the sleeve. These ribs are slightly inclined and have the shape of leaves, the free ends of which rest against the cylindrical bearing surface of the operating member.
The ribs can thus deform and allow the bearing to move radially with respect to the operating element to self-align on the diaphragm during operation.
The self-alignment elastic connecting member is axially secured to the non-rotating ring of the thrust bearing by complementary shapes, by means of a radial flange or of an annular bore situated at its rear end, opposite the diaphragm, and collaborating with a stepped part of the bore of the ring, and of an annular groove formed at its front end and collaborating through complementary shapes with a radial return or the inner ring. An annular bore protecting from the front free end of the operating element forms an axal stop for the axial end of the ribs of the sleeve. The axial end of the sleeve is provided with a sealing lip in rubbing contact with the radial portion of the outer ring.
Sealing makes it possible, on the one hand, to avoid losing the grease which is used to lubricate the rolling bearing and, on the other hand, to prevent the ingress of foreign particles likely to contaminate the inside of the bearing. A sealing flange is arranged at the rear of the bearing and a sealing lip coming from the self-alignment elastic sleeve collaborates at the front of the thrust bearing with a surface of the rotating ring.
While this type of thrust bearing is satisfactory in most cases, it can happen that in certain applications and conditions of use which are extremely harsh in terms of contamination, the sealing may prove insufficient and result in the ingress of contaminants which affect the correct lubrication of the rolling bearing and thereby shorten the life of said rolling bearing.
It is not straightforward, In thrust rolling bearings in which the rings are made of pressed sheet metal, to arrange seals, particularly rubbing seals, very effectively because the often complex shapes and the geometric qualities of the pressed sheet metal rings often make the attachment of such seals awkward.
Furthermore, the quality of the surfaces which act as rubbing surfaces for the lips of the seals is not always very good.
The present invention aims to solve these problems by proposing a compact economical thrust bearing with a low number of parts and which is equipped with effective sealing means.
The clutch-release bearing device of the present invent is of the type comprising an engaging element capable of collaborating with a clutch diaphragm. The engaging element is intended to be mounted on an operating element able to move in translation under the action of a control member, the engaging element comprising a rolling bearing provided with a rotating ring and with a non-rotating ring, the said engaging element being able to move radially with respect to the operating element to allow it to self-align with respect to the diaphragm by virtue of a radially elastic self-alignment sleeve arranged in the bore of the non-rotating ring to collaborate with a bearing surface of the operating element. The bearing is of the conventional type comprising an outer peripheral surface and a bore which are cylindrical and bounded axially by two radial parallel faces, and at least one seal mounted on one of the rings and in rubbing contact with the other ring, the sleeve comprising a sealing means capable of collaborating with a rotating part of the engaging element.
As a preference, the engaging element comprises an engaging piece secured to the rotating ring and able to come into contact with the diaphragm, the sealing means of the sleeve rubbing against a surface of the engaging piece.
In one embodiment of the invention, the engaging piece is integral with the rotating ring.
In one embodiment of the invention, the sealing means of the sleeve comprises a lip formed as an integral part of the said sleeve.
In one embodiment of the Invention, the sealing means of the sleeve comprises a means for forming a narrow passage with a rotating surface of the engaging element.
In one embodiment of the invention, the sleeve is made of rubber.
In one of the embodiment of the invention, the sleeve comprises a metal insert in contact with the non-rotating ring.
Advantageously, the narrow passage is formed between one end of the insert and the engaging element.
Advantageously, the bearing seal is in rubbing contact with a surface-ground surface of the said other ring.
In one embodiment of the invention, the bearing comprises two seals.
In one embodiment of the invention, the sealing means of the sleeve comprises a lip able to come into contact with a rotating surface of the engaging element and a means for forming a narrow passage with another rotating surface of the engaging element.
Thus, the seals of the rolling bearing come into contact with surface-ground surfaces, hence giving very good quality sealing extending the life of the bearing. The sealing means of the sleeve make the ingress of contaminants into the space defined by the engaging piece and the rolling bearing, and therefore into the inside of the rolling bearing, all the more difficult.